Gigantochloa sp. (TH: Krabi) 1

Specimen: BS-0053 [E5] (living plant), Krabi, southern Thailand, received as "ไผ่มัน (phai man), Gigantochloa species" from ธ. ล., 16 Nov. 2011.

Characteristics: Habit tight caespitose. Rhizome pachymorph [n.v.]. Culms straight, erect below, slightly bending outwards above; about 8 m tall [ultimate height not yet known, over 10 m expected]. Young shoots [not yet observed]. Culm-internodes terete, 30–46 cm long, glabrous, mid-green, thinly farinose, thus appearing dull bluish-green; diameter 4 cm [ultimate diameter not yet known]; walls thick, solid or nearly so on the basal culm. Culm-nodes glabrous, smooth, flat; sheath scar marginally protruding, less than 1 mm; supranodal line discernible, without a ridge, about 10 mm above the nodal line; aerial roots none. Branch-buds solitary, from the 4th to 6th node up, subrotund, small, 8–10 mm wide and high. Branches several, the central one dominant; unbranched on the basal and lower culm; branching typically intravaginal on the mid-culm and upper culm, occasionally extravaginal on the lower mid-culm; rebranching. Culm-leaves persistent on the unbranched basal and lower culm, may decay on the culm, late deciduous on the mid-culm and upper culm. Culm-leaf sheaths about 18 cm wide near the base, 27 cm long, half as long to three-quarters as long as the internode; thickly papery, brittle, may tear longitudinally when dry and persistent on the lower culm, straw-colored when dry; covered with short appressed dark brown hairs, black when dry; margins eciliate(?); apex horizontally truncate, 4 cm wide. Culm-leaf auricles 1 mm high entire rims extending from the blade base 1.5–2 cm along the sheath apex towards the edges and forming 3–4 mm high oval-shaped lobes, dark straw-colored when dry, without bristles. Culm-leaf ligule 1–2 mm high, denticulate. Culm-leaf blades thickly papery, late caducous, initially erect, becoming patent, usually reflexed when dry, but may remain persistent and erect on the basal and lower culm, narrowly triangular on the basal and lower culm, otherwise linear-lanceolate, about 1.2 cm wide and 7 cm long on the mid-culm, about a quarter as long as the sheath length, the width of the junction with the sheath 1.2 cm, of the same color as the sheath when dry, hairy adaxially near the base; apex attenuate; margins strongly recurved when dry. Foliage-leaves 6–11 per branchlet. Foliage-leaf sheaths keeled, green, straw-colored when dry, usually glabrous, occasionally with a few appressed short dark hairs; margins eciliate. Foliage-leaf auricles small oval-shaped lobes, dark brownish when young; bristles none. Foliage-leaf ligule about 1 mm high, entire, orange when young; outer ligule small, callus-like. Foliage-leaf blades lanceolate, 19–30 × 2.5–3.5 cm, glabrous on both surfaces, bright green above, pale green beneath; base cuneate to rounded, usually asymmetrical; apex attenuate; margins antrorsely scaberulous; midrib prominent on both surfaces, light green beneath; pseudopetiole about 5 mm long. Flowers and seeds are unknown.

Provisional identification: A species of Gigantochloa. The culm-leaf does not closely resemble any known species of Gigantochloa in Thailand.

Comments: This species is said to be native to southern Thailand, and has been planted as an intercrop in rubber tree plantations (ธ. ล., Krabi, pers. comm., 16 Nov. 2011).